This invention relates to parapulpal dental restorative pins in general, including pins used for taking impressions and making models, as well as pins used for securing restorative materials directly to a tooth understructure. More particularly, the invention relates to a parapulpal dental restorative pins with self-anchoring anti-rotation retention heads, and is applicable to pins of all forms, whether threaded or non-threaded.
Screw-threaded pins for securing dental fillings are disclosed in U.S. Pat. No. 114,454 of Mack and No. 143,418 of Osmond. These early pins were made of metallic wire, gold being mentioned in Osmond. Mack's pin had no head, although he mentions but does not show pins with flattened heads. He simply packed the filling about the pins. Osmond shows a pin with one end split. He packs filling material around the pin to form a base, and then opens the split end of the pin over the base, after which the balance of the filling is made over the base and the opened parts of the split end. He can alternatively open the split end of the pin first, and then pack the filling around it.
This early recognition of a need to retain fillings secured on screw pins from displacement axially along the pins persisted for many years, and is again recognized in U.S. Pat. No. 3,675,329 of Weissman. In a screw pin structure directed primarily to a manipulating portion which is severable, Weissman includes a rounded flanged head for enhancing the resistance against axial displacement of a superstructure relative to the understructure of a tooth.
The prior art includes other forms of pins for anchoring a superstructure or restoration to a tooth. There are, for example, non-threaded pins having a diameter slightly smaller than the hole into which it will be secured, in which case a suitable cement (with which the present invention is not concerned) is used to hold the pin in place. In another form of non-threaded pin, the pin has about the same diameter as that of the hole, and the pin is force-fitted or friction-locked into the hole, to hold the pin in place.